I used about 4 pounds of mix for 3 planters and used the amount of water suggested by the instructions. I mixed it in a plastic bucket with a garden trowel. I added the mix to the mold, a little bit at a time, while tapping the mold to try to prevent air pockets. Remember to wear your gloves, mask, and safety glasses!
I cured the concrete for the amount of time the instructions suggested for warmer weather. During this time, I tried to keep the concrete moist. After I removed the concrete from the molds, I soaked the planters in water and vinegar overnight to try and neutralize the concrete.
The bottom of my planters were not completely level, so I sanded them down using a bit of sand and a plank of wood.